Locking thread supply case for sewing machines



July 23, 1940. w T, MINETT 2208,999

LOCKING THREAD SUPPLY CASE FOR SEWING MACHINES Filed Feb. 28, 1938wines; ,fin /enior" Patented July 23, 1940 UNITED STATES PATENT OFFICELOCKING THREAD surety CASE FOR SEWING MACHINES New Jersey ApplicationFebruary 28, 1938, Serial No. 192,915

8 Claims.

The present invention relates to lockstitch sewing machines, and moreparticularly to improvements in thread cases for holding a supply oflocking thread within a hollow 100p taker of the 5 rotary hook type,similar to that disclosed in U. 8. Letters Patent to Ashworth No.1,169,909 of February 1, 1916, and to the present inventor No. 1,895,257of January 24, 1933.

In the machines of the patents above referred to. a thread case ofdiscoidal shape is provided and the needle loop, as it is passed aboutthe thread case by the loop taker, frequently assumes an irregularposition so that an excess of needle thread is required for smoothpassage of the needle loop. To provide the required amount of needlethread in all circumstances, the motions of the other stitch formingdevices and principally those of the take-up must be so adjusted thatthe needle thread will be given up at a to greater rate after a stitchis set than is required when the needle loop passes in a regular mannerover the thread case. With the stitch forming devices so adjusted. thetension in the thread of the needle loop as it passes over the threadcase 26 will increase when the loop assumes an irregular position on thethread case and the uniformity with which successive stitches are set inthe work may be affected adversely. It has been observed that thisdifficulty is due at least in a 30 part to a failure of a needle loop tostart its movement about the thread case, at a definite predeterminedinstant with respect to the movement of the loop taker and to that ofthe other stitch forming devices. Another factor which 85 contributes tothe difficulty is the accumulation of wax, strands of thread and otherparticles within the space between the thread case and the loop taker insuch a way that the movement of the needle loop will be retarded orjammed 40 between the loop taker and thread case.

The principal object of the present invention is to provide a novel andimproved locking thread case for use within a loop taker of the rotaryhook type, wherein the nedle loop does not pass I over the loop taker,so arranged that the difiiculties referred to are avoided, each needleloop being caused to pass over the thread case smoothly and uniformlywithout requiring the other stitch forming devices to give up anexcessive l0 amount of needle thread and without the provision ofexcessively large clearance spaces between the thread case and the looptaker to avoid retarding or jamming of the needle loop from accumulationof wax or other matter.

I. With these and other objects in view. the lnvention is hereinafterdescribed as embodied in a hook needle lockstitch sewing machine havinga discoidal thread case formed with flat end and curved side surfaces,so arranged as to be held from rotation within the loop taker. of meanson the side of the thread case for causing the needle loop to start itsmovement over the thread case uniformly when the loop taker reaches apredetermined angular position. In the form of the inventionillustrated, the thread case has a relatively large thread holdingcapacity similar to that disclosed in inventors patent above referredto, and the means for starting the needle loop over the thread caseconsists of a thread guiding shoulder extending from a location on 16the side of the thread case close to the path traversed by the tip ofthe loop taker beak to an end surface on the thread case.

The several features of the present invention and other advantagessecured thereby will be readily understood by those skilled in the artfrom an inspection of the accompanying drawing and the followingdescription.

Referring to the drawing. Fig. 1 is a view in ide elevation and partlybroken away of portions of a lockstitch sewing machine embodying theloop starting shoulder of the present invention; Fig. 2 is a sectionalplan view of the same parts of the machine; and Fig. 3 is an enlargedview of the loop starting shoulder on the thread case, shown in section,taken along the line 3-3 of Fig. 1.

The machine illustrated in the drawing is of substantially the sameconstruction and manner of operation, except as hereinafter pointed out,as that disclosed in the patents referred to. The machine includes acurved hooked needle ID, a work support l2, a presser-foot H, a rotaryloop taker i6, a thread case l8, and other stitch forming and workfeeding devices. The loop taker 4o consistsiof a hollow cylindrical bodyhaving a rotary hook or beak, the tip 20 of which is-arranged to entereach needle loop, indicated at 21, after being opened by a loop spreader(not shown) and to carry each loop about the thread 5 case It. The looptaker is also formed with two guiding grooves or raceways 22 and 24 forrotatably supporting the loop taker in the machine frame and forsupporting the thread case it within the loop taker, respectively.

The raceway groove 24 is engaged by a circular flan e 26 on the sidesurfaces of the thread case, the thread case being discoidal in shapewith cyliggrical curving side surfaces between two subst tially flat endsurfaces. One end of thethreadcaseisclosedwithanendwallfrom which thereprojects a stud 25 for receiving a wound bobbin or cop for the lockingthread indicated at 28. The other end of the thread case is left open toprovide access to the inside, the end surfaces of the side walls onlybeing p sed. For holding the thread case from rotation with the looptaker, a pair of alternately reciprocating pins or fingers III areprovided slidingly mounted in a fixed part of the machine and engaged bya rat trap spring 32 to'force the pins into slots at one end of thethread case, each pin being lifted to clear the needle loop as it passesacross the open end of the thread case.

The tip 20 of the loop taker beak is so arranged that in engaging theneedle loop and carrying it about the thread case it gives the needleloop a half twist, the loop being drawn forwardly of! the tip of thebeak by the action of the take-up after the circuit has been completed.In this way the needle loop is passed about the thread case withoutpassing entirely over the loop taker. To facilitate passage of theneedle loop the axis of rotation of the loop taker is inclined towardsthe surface of the work and towards the rear of the machine. The threadcase is almost completely enclosed within the hollow of the loop takerand, in order to provide space for a relatively large quantity oflocking thread without increasing the outside diameter of the looptaker, the thread case is of such diameter as to fit closely within thehollow of the loop taker. One side of the needle loop 2|, as drawn bythe loop taker beak, passes over the outside of the loop taker, and theother side into a space 34 provided by a cut-away portion of the threadcase side wall between the ends of the raceway flange 26. The flange 26has a hook or notch 21 at one end to assist the loop taker beak inseparating the two sides of the needle loop and to hold from rotationwith the loop taker that side of the needle loop within the opening 34.

In the machines of the patents, that side of the needle loop held withinthe opening 34 after being disengaged from the needle is caused to passacross the open end of the thread case and the other side of the needleloop is caused to pass across the closed end of the thread case. As thenotched end of the flange is engaged by the needle loop, it sometimes iswound partway about the curved side surfaces of the thread case beforeit begins to move across the open end. When this occurs, more needlethread will be drawn by the loop taker as it passes the needle loop overthe thread case than when the needle loop begins to pass across the openend of the thread case directly after the loop taker engages it. As aresult, the other stitch forming devices must be so adjusted that theamount of needle thread available is sufllcient to allow the loop topass over the thread case, even when it is wound about the curved sidesurfaces of the thread case, before starting across the open side. Whenthe stitch forming devices are adjusted in this manner, if the needleloop starts across the open end of the thread case at once after theloop taker engages it, there will be a surplus of thread so that eachstitcl. being formed will not be set withjthe same degree of tension orthe needle thread as it extends along the surface of the work betweenstitches will not be drawn uniformly tight before the succeeding stitchis completed. 5

To cause the needle loop to begin its knovement across the open end ofthe thread caseihuniformly at a definite point, in accordance with I epresent i f I invention, in the operation of the loop taker in carryingthe needle loop about the thread case, the circular side wall of thethread case along the cut-away portion adjacent the notched end of theflange 28 is formed with an inclined and grooved or under-cut threadguiding shoulder 36 extending at an angle from the notched end of theflange 2G to the end surface of the side wall at the open end of thethread case. The inclination of the grooved shoulder 36 and the pointalong the end surface of the thread case at which the shoulder 36terminates are so chosen that the needle thread, as the loop is firstengaged by the loop taker, will lie smoothly within the groove of theshoulder, the shape of the groove being such that the thread is drawntowards the inside of the thread case away from the inside of therotating loop taker. As soon as the loop taker reaches a position wherethe thread of the needle loop is carried above the end of the shoulder,the side of the needle loop begins to cross the open end of the threadcase so that there is a definite predetermined movement of the needleloop as it is being passed around the thread case.

The groove in the shoulder 36, as more clearly illustrated in Figure 3,forms a sharpened edge 38 on the shoulder which acts not only to shiftthe thread away from the inside of the loop taker, but also to scrape onparticles of wax, strands of thread, or other foreign substances whichmight tend to retard or jam the thread between the thread case and theloop taker. The inside of the loop taker, therefore, is kept clear andsince the amount of thread required by the loop taker in the needle loopis uniform during each cycle, there is no necessity for providing anexcess of thread during the passage of the needle loop about the threadcase. The tension on the needle thread during successive stitches isthus kept more nearly uniform with the resultant advantages inuniformitywith which the stitches are formed and set.

Having thus described the invention, what is claimed is:

1. A lockstitch sewing machine having, in combination with other stitchforming devices, a hook needle, a discoidal thread case having flat endsurfaces'and a curved side surface, a loop taker for passing each loopof needle thread about the thread case without itself passing throughthe loop, means for holding the thread case from rotation with the looptaker, and means on the side surface of the thread case for causing oneside of the needle loop to begin moving across an end surface of thethread case when the needle thread carried by the loop taker reaches apredetermined position with respect to the thread case.

2. A lockstitch sewing machine having, in combination with other stitchforming devices, a hook needle, a discoidal thread case having flat endsurfaces and a curved side surface, a loop taker for passing each loopof needle thread about the thread case without itself passing throughthe loop, means for holding the thread case from rotation with the looptaker, and a thread guiding shoulder on the thread case extending from alocation close to the path traversed by the tip of the loop taker beakto an end surface of the thread case for causing one side of the needleloop to begin moving across said surface when brought into engagementwith the shoulder by the loop taker.

3. A lockstitch sewing machine having, in combination with other stitchforming devices. a

hook needle, a hollow rotary loop taker, a discoidal thread case havinga flange along its curved side surface slidingly mounted within araceway groove inside the loop taker and arranged with a notched end toseparate the sides of the needle loop carried by the loop taker as theloop taker passes around the thread case, and a grooved thread guidingshoulder on the thread case extending from the flange to a point at oneedge of the curved side surface of the thread case for causing one sideof the needle loop to begin moving radially across the thread case at apredetermined position of the loop taker.

4. A lockstitch wax thread sewing machine having, in combination withthe other stitch forming devices, a hook needle, a rotary loop takerhaving a circular hollow opening and a raceway groove inside theopening, a discoidal thread case having a circular flange rotatablewithin the groove in the loop taker and a curved side surface extendinginto the opening in the loop taker beyond the groove and fitting closelythe inside of said opening, and means on the thread case beyond theflange for clearing the inside of the loop taker of material tending tojam between the thread case and the loop taker.

5. A lockstitch wax thread sewing machine having, in combination withthe other stitch forming devices, a hook needle, a rotary loop takerhaving a circular hollow opening and a raceway groove inside theopening, a'discoidal thread case having a circular flange rotatablewithin the groove in the loop taker and a curved side surface extendinginto the opening in the loop taker beyond the groove and fitting closelythe inside of said opening, and a sharp-edged the curved side surfacebeing provided with a thread engaging notch positioned intermediate theend faces and having an inclined thread guiding shoulder extending fromthe notch to an end face to guide one side of the needle loop from thethread notch to said end face, and a loop taker for causing the needlethread loop to pass around the thread case.

'7. A discoidal locking thread case for lockstitch sewing machinesemploying a hooked needle, said thread case having end faces and acurved side surface therebetween, a thread engaging notch on the curvedside surface, and a thread guiding shoulder extending from the bottom ofthe notch to one of the end faces.

8. A discoidal locking thread case for lockstitch sewing machinesemploying a hooked needle,said thread case having end faces and a curvedside surface therebetween, an interrupted peripheral flange spaced fromone of the end faces and terminating in a thread engaging notch, and aninclined, grooved thread guiding shoulder extending obliquely from thebottom of the notch to said end face and spaced radially inwardly of theflange.

WILFRID THOMAS MINETT.

